Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterised by the progressive deterioration of upper and lower motor neurons and atrophy of skeletal muscle. Despite advances in genomics methods that have enabled the identification of many ALS risk variants, these account for just 20% of cases. However, many of the associated genes are implicated in mechanisms of RNA homeostasis, inflammation, protein degradation, and vesicular transport, thus providing clues to the underlying pathological pathways involved in the disease. Skeletal muscle is a strongly affected tissue in ALS, and changes in muscle physiology, including chronic denervation and reinnervation of muscle, as well as neuromuscular junction dismantling, are amongst the earliest pathological processes that occur in the disease. Skeletal muscle is now a recognised secretory organ, releasing molecules that can act in an autocrine and endocrine manner. These molecules have been coined myokines and are well established players in intercellular signalling. Muscle has also been shown to secrete extracellular vesicles including exosomes, and these muscle vesicles (MuVs) have been shown to contain cargo proteins, miRNAs and lipids that can alter cellular mechanisms in recipient cells. Indeed, MuVs isolated from ALS patient cell cultures have recently been reported to exert significant levels of toxicity when added to iPSC motor neurons. The work detailed in this thesis contributes further evidence implicating MuVs in ALS pathology, including confirmatory experiments illustrating the neurotoxicity of ALS MuVs to healthy iPSC motor neurons, and demonstration that candidate biomarkers, first identified in MuVs isolated from primary muscle cells, are also increased in the serum of ALS patients. Furthermore, this work describes both a novel immunocapture technique that permits isolation of MuVs from patient serum for the downstream detection of candidate biomarkers, and a MuV lipid quantification assay as a potential biomarker candidate in ALS.
- Neuromuscular disease